docs: def write(self, data, debug_info=None):
          """
          Write data to YHSM device.
          """
          self.num_write_bytes += len(data)
          if self.debug:
              if not debug_info:
                  debug_info = str(len(data))
              sys.stderr.write("%s: WRITE %s:\n%s\n" %(
                      self.__class__.__name__,
                      debug_info,
                      pyhsm.util.hexdump(data)
                      ))
          return self.ser.write(data)